Drill bit



Feb. 22, 1938. M |-|QKAN$QN 2,109,390

DRILL BIT Filed June 13, 1935 3 Sheets-Sheet 5 INVENTOR. yaw/3x.

ATTORNEY.

Patented Feb. 22, 1938 UNITED STATES PATENT OFFICE Martin flokansom l l ii tht l i finn assignor to Eidco, Inc., Duluth, Minnesota Minn, a corporation. of.

Application June 13, 1935, Serial No. 26,418

10 Claims. (01. 255-64) This invention relates to improvements in drill bits and to that class of drilling encountered in rock boring or the like, such as that set forth in my Patent No. 1,589,596 issued to me on June 22, 1926.

, The principal object of my present invention is that of providing means whereby suitable reinforcement for the strength of the cutting edge of the bit is provided, thus increasing the efficiency and durability of such a bit.

Another object is to provide against unequal wear in such a bit, and at the'same time maintaining a form of cutting edge most convenient for sharpening.

Another object is to 'make a bit inv which the peripheral part of the cutting edge will lead or be cutting ahead of the remainder of the cutting edge and at the same time maintain cgnvenience in sharpening the cutting edge of the bit when necessary.

Still another object is to provide a more practical arrangement of circular cutting edges than disclosed in my former patent, supra.

Other objects and advantages of the invention will appear in the following description thereof.

Referring now to the accompanying drawings, forming part of this application, and wherein like reference characters indicate like parts:

Figure 1 is a central vertical sectional view through a twin circle bit of the improved type.

Figure2 is a plan view of the face of the bit shown in Figure 1.

Figure 3 is a view similar to Figure 1 of a twin curve bit having a concaved or semi-cylindriform face the axis of which intersects at right angles the axis of the bit.

Figure 4 is a plan view of the face of Figure 3.

Figure 5 is a view similar to Figures 1 and 3 of a twin curve bit having a segmental spherical concaved face. v

Fig. 5a is a vertical central sectional view on the line 5a-5a, Figure 5.

Figure 6 is a plan view of the face of the bit shown in Figure 5.

Figure '7 is a'view similar to Figure 1 of a twin curve cutting faced bit having an inverted V- 'shaped channel, the apex of which is at right angles to the axis of the bit.

Figure8 is a plan view of the face of the bit shown in Figure 7.

Figure 9 is a central vertical section through a tripple circle cutting faced bit, on the line 99,

' Figure 10.

Figure 10 is a plan view of the face of the bit shown in Figure 9.

Figure 11 is a central vertical section of "a quadruple circle cutting faced bit, on the line H-ll, Fig. 12.

' Figure 12 is a plan view of the face of the bit shown in Figure 11.

Figure 13 is a transverse sectional view on the line l3-l3, Figure 12, illustrating the reinforcing shoulder which comprises the major feature of the instant invention.

It is obvious to those skilled in the art that the matterof strength, efllciency and durability are essential in such an instrument as well as provision for suiilcient stock for repeated sharpening when necessary and to'provide the walls of the cutting edge of suflicient size to withstand the impacts while cutting.

The construction shown in my former patent, supra, is somewhat lacking in this latter respect, in that the illustration shows only pairs of cutting circles of different diameters in a single drill head, but in my improved type of drill bit I have found that it is essential for best results that the cutting circles or curves in each bit be of identical size.

The type of drill bit shown in the first eight figures of the accompanying drawings, embodying the twin circle or curve cutting bit, is that preferred for drilling in softer material in view of the large proportion of clearance for the bit, which, in this instance, is nearly 50% of the area of the hole being drilled; while, for drilling in harder material, the three-circle or curve bit would beused, and when drilling the hardestv material the four or more circle or curve bit, is preferred.

It is to be understood, and as thought clearly illustrated in the drawings, that the depressions within the faces of all of the bits illustrated are of conical form, the variation of the patterns of the cutting edges formed thereby occurring simply by the relative relation of the axes of the cones to the axis of the bit, and the concavity of the face of the bit, whether formed by an inverted V surface, a cylindriform surface, or by a segmental spherical surface.

However in all of these types it is comparatively siinple to provide reinforcement for the cutting edge, which at first glance may seem fragile, by increasing the thickness of the stock transverse each circle or curve in outward direction of .its radial center, as clearly illustrated at I in the drawings; this reinforcement in the body of the cutting edge being substantially constant in all the types of faces employed except as said reinforcement approaches the extreme outside periphery of the bit as at I3 in Figs. 2, 4, 6, 8, 10, and 12 in which case it rapidly is decreased to nil as shown at 2 and 3 in Figures 2, 4, 6, and 8, and at I4 in Figs. 10 and 12; this whether straight, concave or inverted V-shape, as the case may be. It is quite apparent that at the point where the peripheral edge of any one of the circular or curved cutting edges becomes tangential to the wall of the hole being made is the weakest point of the instrument, and inclined to wear away more rapidly than the reinforced portions of the cutting face.

In the modified form of bit shown in Figures 3 to 8, wherein the face of the bit is hollowed out either by an inverted V surface as shown at 4, Fig. 7, or a cylindriform surface as at 5, Fig. 3, the axes of either of which is at right angles and coincident to the axis of the bit, or by a segmental spherical concavity as at 6, Fig. 5, the center of which is coincident with the axis of the bit, resulting in two opposed extreme cutting portions 2 and 3 materially leading in the cutting operation, so that as the cutting progresses and the more sensitive part of the cutting face of the bit wears away slightly faster than the remainder thereof it may be readily sharpened without in any material way affecting the cutting nature of the bit; it beingunderstood that the sharpening operation of the inside of the conical depression is accomplished by a cone shaped end grinder. It is also obvious that the segmental spherical or spheroidal concavity is applicable to all forms of bits herein illustrated or described. It will be noted that in the modified form of two circle or curve bit shown in the last mentioned six views the apexes I of the cone shaped depressions are closer to the axial line of the bit than that shown in Figures 1 and 2, yet they can be sharpened in a like manner; that is by a cone shaped end grinder.

It is quite well known that minerals which are subject to crystallization have cleavage surfaces, and that these cleavage surfaces vary with the system of crystallization. Considered from a strength standpoint, the cleavage surfaces are the weak part of the mineral. When, therefore, subjected to cutting or crushing the mineral will probably break along the cleavage surfaces.

It has been found that drilling in certain mineral formations, a bit shaped like that illustrated in Figures 3, 4, 5, 6, 7 or 8, or multi-circles or curves thereof, may out faster than a straight face bit with multi circles or curves such as illustrated in Figures 1, 2, 9, 10, 11, and 12.

It is obvious that the cutting edge formed by the intersection between the cones forming the depressions in the face of the bit and the inverted V surface, or the cylindriform surface, or spherical or spheroidal surfaces have different characteristics relative to the speed of cutting, efiiciency, and durability of the bits when drilling in a mineral with pronounced cleavage surfaces and which can only be determined by actual tests in each case.

It is also obvious that the angle formed by the inverted V surface with its apex at right angles and coincident to the axis of the bit as shown in Fig. 7 can be varied between zero and the angle formed by the cones to the same plane.

In the same manner the radius of the cylindriform surface or the spherical or spheroidal surfaces can be varied in such a manner that either the above surfaces becomes tangential to the cones or becomes a flat surface at right angles to the axis of the bit.

It is to be further understood that in both the three and four or more circle or curve types, the cone shaped end grinder is also employed not only for the sharpening of the circles or curves but also within the axial feed-hole III of the bit so that, as illustrated in both Figures 10 and 12, the tangential meeting point of the circles about said center are somewhat remote therefrom but insuring perfect grinding of the entire cutting edge of each circle or curve; as an example this results in the triangularly shaped recess I I in the three circle bit and in the square recess I2 in the four circle bit. It is obviously essential that the cutting edges be true, and that the sharpening occur at the proper tangential point of the circle or curve.

It will be further noted that in these last two types mentioned, where the cone end grinder is used axially therein additional clearance is provided to each circular portion of the bit from the central water supply. It is also noted that there is ample clearance in this construction of-bit, having a plurality of equally sized circular or curved cutting edges, and that the reinforcing shoulder I may be made greater, lesser, or exactly equal to the angle of the cone to the vertical.

The type of bit herein illustrated and described is particularly adapted as a detachable bit such as used in jack hammers and drifting machines and the like for drilling in rock or other similar material; but it may also be adapted to nondetachable bits for the above purpose as well as in the larger percussion bits used in open quarries, oil well drilling, open pit mines, etc.

Having thus described my invention, what I claim and desire to secure by Letters Patent,-is:

1. A drill bit of the type described having a concave'cutting face consisting of a plurality of equally shaped cutting edges, said concavity being formed by the intersection of a spherical surface and cones with axes parallel with the axis of the bit.

2. A drill bit of the type described having a concave cutting face consisting of a plurality of equally sized substantially elliptical cutting edges, said concavity being formed by the intersection of inclined plane surfaces and cones with axes parallel with the bit axis.

3. A drill bit of the type described having a concave cutting face consisting of a plurality of equally shaped cutting edges, said concavity being formed by the intersection of a cylindrical surface with axis at right angles to the bit axis and coincident therewith, and cones with axes parallel with the bit axis.

4. A drill bit of the type described having a cutting face consisting of a plurality of equally sized and shaped continuous cutting edges spaced equally about the bit axis, said cutting edges being integrally formed in said face by the intersection of oppositely disposed inclined surfaces, the area of the outer inclined surfaces progressively decreasing toward the most distant point of said cutting edges from the bit axis.

5. A drill bit having a face provided with a plurality of continuous cutting edges, each formed by a conical depression in said face, no two adjacent points of said edges being in a plane at right angles to the axis of the bit, and said cutting edges being equally spaced about the axis of the bit.

6. A drill bit having a face provided with a plurality of similarly shaped continuous cutting edges equally spaced about the bit axis, the most distant point of each cutting edge from the bit axis leading in the cutting operation.

'7. A drill bit having a face provided with a plurality of similarly shaped continuous cutting edges equally spaced about the bit axis, the most 9. A drill bit having a face provided with a plurality of continuous cutting edges, equally spaced about the bit axis, said cutting edges being formed by the intersection of oppositely disposed inclined walls, the outer walls of each cutting edge progressively decreasing toward that point of each cutting edge farthermost from the bit axis.

10. A unitary drill bit having a face provided with a plurality of equally sized and shaped continuous cutting edges, the axes of which are equally spaced from and about the bit axis, said cutting edges being formed by the inter-section of oppositely disposed inclined walls, the outer walls of each cutting edge progressively decreasing toward the most distant point of said cuttin edge from the bit axis.

MARTIN HOKANSON. 

